FWIW -

in terms of statistical sampling practices if you need a mean and standard deviation what you are doing is really overkill, and results in a sample size of 50% of the data.
You might just as well mean/std deviation/ANOVA or whatever the whole file.

For example, a statically signficant (95% confidence) sample size for the population of the US used in polling: ~1526 persons taken out of 300 million using systematic sampling methods. What you are doing is sort of systematic sampling, yes, but the intent of sampling is not to look at almost everything.